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DePaul: Deconstructing post-exertional malaise: An exploratory factor analysis

mango

Senior Member
Messages
905
Deconstructing post-exertional malaise: An exploratory factor analysis

Stephanie L McManimen, Madison L Sunnquist, Leonard A Jason
DePaul University, USA

Abstract
Post-exertional malaise is a cardinal symptom of myalgic encephalomyelitis and chronic fatigue syndrome. There are two differing focuses when defining post-exertional malaise: a generalized, full-body fatigue and a muscle-specific fatigue.

This study aimed to discern whether post-exertional malaise is a unified construct or whether it is composed of two smaller constructs, muscle fatigue and generalized fatigue. An exploratory factor analysis was conducted on several symptoms that assess post-exertional malaise.

The results suggest that post-exertional malaise is composed of two empirically different experiences, one for generalized fatigue and one for muscle-specific fatigue.

Keywords: chronic fatigue syndrome, factor analysis, myalgic encephalomyelitis, operationalization, post-exertional malaise

http://hpq.sagepub.com/content/early/2016/08/23/1359105316664139.abstract

Leonard Jason on Facebook said:
Newest online publication from the DePaul group:

McManimen, S. L., Sunnquist, M. L., & Jason, L. A. (2016). Deconstructing post-exertional malaise: An exploratory factor analysis. Journal of Health Psychology, 1-11. Published online August 25, 2016. doi: 10.1177/1359105316664139
https://www.facebook.com/leonard.jason.12/posts/10208456959794536
 
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Invisible Woman

Senior Member
Messages
1,267
I appreciate the guys at DePaul are some of the good ones but .... AGAIN with the fatigue.....

Fatigue is just a small part of PEM or PENE in my experience and is secondary to neuro symptoms and excruciating, abnormal muscle pain and weakness among other much nastier symptoms.
 
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2,158
Is there any way of accessing the full article? And is it worth the effort anyway?
I notice that the abstract uses the word 'fatigue' to describe both sorts of PEM. This rings alarm bells for me because it seems another instance of trivialising the reality of PEM, and hence of ME in the same way as renaming ME as CFS has done.
For me I guess you could say there are two aspects to PEM.
1. If I have overused one particular muscle group, eg legs from standing, or arms/shoulders from writing, I get greatly increased pain and weakness, and sometimes shaking or twitching in those muscles that can last for days.
2. If I have done anything physical beyond my low threshold - whole body symptoms that can last days or weeks - flu-like symptoms - headache, nausea, dizziness, sore throat, overall weakness and pain in all muscles, inability to think straight or concentrate etc.
The word 'fatigue' doesn't begin to describe these PEM symptoms.
What do others think?
 

Snow Leopard

Hibernating
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5,902
Location
South Australia
Sorry for the lost formatting, I hope this is clear. The main results:

Table 1. Factor loadings for each post-exertional malaise item (N = 648).
General Fatigue factor loadings:

Post-exertional malaise(a) .832
Prolonged generalized fatigue or malaise following previously tolerable levels of exercise(a) .822
Post-exertional exhaustion that is immediate or delayed(b) .820
Symptoms worsen with exertion(b) .816
Substantial reduction in pre-illness activity level due to low-threshold physical and mental fatigability(b) .758
Fatigue or extreme tiredness(c) .715
Marked, rapid physical or cognitive fatigability in response to exertion(b) .688
Exhaustion not relieved by rest(b) .666
Prolonged worsening of symptoms after physical activity(d) .612
Minimum exercise makes you physically tired(c) .609
Physically drained or sick after mild activity(c) .576
Mentally tired after the slightest effort(c) .529
Muscle fatigue factor loadings:
Muscle weakness after minor exertion(d) .926
Muscle fatigability after minor exertion(d) .906
Muscle pain after minor exertion(d) .810
Next day soreness or fatigue after nonstrenuous, everyday activities(c) .420
Dead, heavy feeling after starting to exercise(c) .409

Notes:
ME-ICC: ME International Consensus Criteria; ME: myalgic encephalomyelitis; DSQ: DePaul Symptom Questionnaire.
(a)CDC (Reyes et al., 2003).
(b)ME-ICC (Carruthers et al., 2011).
(c)DSQ (Jason et al., 2010).
(d)Ramsay (Ramsay, 1988).

Also reported in tables was:
Correlation and mean factor scores by demographic and functional status
Percentage of patients meeting a 2–2 threshold for PEM symptoms

But you'd have to read the actual paper to see those...

edit:

Demographic characteristics:
The sample (N = 704) was predominantly female with just 10.3 percent male participants.
Most participants were Caucasian (96.4%), and only 2 percent identified themselves as being of
Latino or Hispanic origin. For marital status, 56.4 percent were married or living with a partner,
2.6 percent were separated, 1.1 percent widowed, 13.4 percent divorced, and 26.5 percent never married.

So looking at the above, it looks like a substantially biased (convenience) sample...
 
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2,158
Thanks everyone, looks like while I was busy writing my comment, others had done as I asked and made the same point! Great minds!
 
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15,786
They seem to be focusing on questionnaire items which best represent the experience of PEM:
PEM items.jpg


Interesting that the items from Jason's own questionnaire get the worst ratings :p Hopefully he'll be able to understand the descriptions of PEM some day.

They're also looking at patient characteristics versus their two types of PEM responses, such as ability to work. Generally a positive piece, but as usual, completely the wrong focus on fatigue.
 

Mij

Messages
2,353
If it was the questionnaire I tried to fill out a couple of years ago I'm not surprised, the way the questions were structured it was as though I was reading the SAME questions over and over again about how fatigue affects us. I was becoming dizzy and gave up. It gave me PEM.
 

JohnCB

Immoderate
Messages
351
Location
England
Fatigue? FFS :bang-head:

Full text at http://hpq.sagepub.com.sci-hub.cc/content/early/2016/08/23/1359105316664139.full.pdf html

It actually looks better (at least the beginning does), so it might just be a really poor choice of words in the abstract.

I felt that the whole introduction section was a very useful discussion of PEM/PENE. I am not going to comment here whether there was too much emphasis on fatigue; the word gets used so many different ways and seems to cover a range of concepts. However personally it is about pain and brain fog and symptom exacerbation as a whole.

What they did was give a better overview of this subject than I recall seeing elsewhere. I certainly felt that I learnt a better understanding by taking the time to read this. I also found it interesting that the responses were different if asking about "exercise" or "daily activity". The discussion of what PEM was understood to be by the different authorities (Ramsay, Holmes, Goudsmit, etc.) was also useful for me.

At this point I have not yet read the results. That is a joy for later, PEM allowing.
 

BruceInOz

Senior Member
Messages
172
Location
Tasmania
In the Results section, the paper says:

Factor extraction and determining the number of
factors to be retained.
A total of 54 participants
were excluded from the factor analysis due to
incomplete data. Principal axis factoring was
used with an oblique rotation (promax). An
examination of eigenvalues (>1) and the scree
plot suggested a two-factor solution; only two
factors had eigenvalues >1.

Later they say they identified Factor I as a General factor and Factor II as a Muscle factor. I don't really understand how they did this, but it sounds like their numerical analysis of the responses grouped the questions into two distinct groups which they identified as General and Muscle. However, none of the questions ask only about mental fatigue - it is always lumped in with eg., "physical and mental" fatigue. Surely if they wanted to analyse factors like this they should have had questions that asked about mental fatigue only, in which case might they have discovered another factor. Since they took the questions from existing instruments, this may reflect a deficiency in those instruments,

Just another example that seems to show that researchers don't get all the issues confronting us.
 

Dolphin

Senior Member
Messages
17,567
With the variety of questions utilized to assess PEM, how a question is phrased is also of importance, as different phrasing can illicit varying responses. However, many patients attempt to reduce the frequency and severity of their PEM by pacing themselves and staying within their energy limits (Jason et al., 2009). As a result, they may not be currently experiencing PEM. This, in turn, could affect the way patients respond to certain subjective questions. Jason et al. (2015a) found that 25 percent of the participants would respond “no” to the question, “Do you feel generally worse than usual or fatigued for 24 hours or more after you have exercised?” Yet, of those who answered “no,” all of them answered “yes” to the question, “Do you experience high levels of fatigue or weakness following normal daily activity?” This finding indicated that the specificity of the first question, requiring 24 hours of fatigue and mentioning exercise, resulted in many patients not being counted as having PEM. Additionally, Jason et al. (1999) noted that the endorsement of PEM ranged from 40.6 to 93.8 percent of a group of individuals, depending on how the question was phrased.
 

Dolphin

Senior Member
Messages
17,567
These findings indicate that more frequent and severe symptoms are associated with worse functioning.
This is something I have noticed. When this pattern is off, I look out for comorbidities or alternatively alternative diagnoses.
 

Dolphin

Senior Member
Messages
17,567
Symptom presence

A symptom was determined to be present if it was present for at least half of the time (frequency ⩾ 2) with moderate severity (severity ⩾ 2) over the past 6 months (a 2–2 threshold). Table 3 shows the percentage and number of participants who have each symptom at the required threshold. Almost all of the participants, 99.6 percent, had at least one of the PEM symptoms. Additionally, 94.9 percent had at least one symptom from the Muscle factor and 99.3 percent had at least one symptom from the General factor. For the participants who did not meet at least one item in the Muscle factor, the functioning level was significantly higher than those who did meet one item in both the Bell Ability Scale (F(1, 591) = 39.16, p < .001) and the SF-36 Physical Functioning subscale (F(1, 591) = 35.57, p < .001). Additionally, 47.2 percent of those who did not meet at least one muscle symptom were able to work at least part-time compared to 21.2 percent of the participants who did have at least one muscle symptom present at the 2–2 level. A Fisher’s exact test showed that the group that did not meet any Muscle factor symptoms were significantly more likely to work at least part-time, p < .001.
 

Dolphin

Senior Member
Messages
17,567
Additionally, several significant differences were found when analyzing the association between factor scores and level of functioning. There were significant negative correlations between both factors scores and the SF-36 Physical Functioning subscale and the Bell Ability Scale. These results indicate that, as expected, more frequent and severe symptoms are associated with worse functioning.

Interestingly, there were significant differences in mean factor scores when examining marital status, education level, current work status, and household income. The scores for the individuals who can work outside the home were lower, indicating less impairment, than those of individuals who were unemployed or on disability. This finding suggests that as symptoms become more frequent and severe, the ability to work outside the home declines.
Possibly useful in some form, as shows that not working is not simply a choice made by people who are no different in terms of impairment to people who are working.

Similarly, this could explain the differences found between the patients with college degrees and the patients who completed high school or less. Bakken et al. (2014) found two age peaks in the incidence of ME and CFS in a Norwegian population, 10–19 years and 30–39 years. For individuals who developed ME or CFS during the earlier peak, the severity of the illness may have prevented some patients from completing a higher education.
 

Dolphin

Senior Member
Messages
17,567
Reasonable exploration of possible interpretations of this finding, it seems to me:
There was a general trend of mean factor scores decreasing as income levels increase for both factors, which may have several possible explanations. First, patients with higher household incomes may be able to find specialized treatment for their symptoms. These individuals would have the means to travel to specialists or see physicians who are not covered by their insurance. This would allow them to find the effective treatments sooner, which could help to lessen their symptoms. Additionally, a higher household income could allow for several resources and supports that would permit the patient to exert themselves less or pace better (i.e. stay within their energy envelope), which could result in experiencing PEM less than those individuals who do not have this financial support system. Such factors could include being able to work less outside the home, afford access to higher quality healthcare, afford better quality food, and employ assistants to help with household tasks or help with daily care for the patient. Deale and Wessely (2001) found that many patients are unsatisfied with the level of care they receive and often report disagreement on the diagnosis, receive a misdiagnosis, or experience dismissive or unknowledgeable doctors. Patients with higher income may be able to travel further or pay to see out-of-network physicians who specialize in ME and CFS care, which could help reduce the severity of their symptoms since the physician is knowledgeable about possible treatments or pacing. Alternatively, it is possible that individuals with lower factor scores, less frequent and severe symptoms, are physically well enough to hold employment, thus leading to an increase in household income.

Contrast this with how many CBT school researchers discuss supports people get or could get
 
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Dolphin

Senior Member
Messages
17,567
The differences found between married or living with a partner and the individuals who are separated, divorced, or widowed may suggest that a lack of family support has negative consequences for the course of ME and CFS. Schweitzer et al. (1995) found that 43 percent of CFS patients reported that their family initially did not accept their diagnosis as being a valid illness, which caused a strain on their relationships. However, once the family accepted the illness as being legitimate, they would help provide care and support when symptoms become more severe and affected functioning. Additionally, it is possible that some of the patients who are not married or living with a partner may not have had the energy available to maintain relationships or have been abandoned by partners due to their illness severity. Patients who do not have this social support built into their everyday lives due to divorce, separation, or death of a spouse may not have the means to take care of themselves during periods of increased illness severity. As a result, they may have to continue over-exerting themselves, thus exacerbating their symptoms even further.
Again, contrast this with how many CBT school researchers discuss supports people get or could get
 
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alex3619

Senior Member
Messages
13,810
Location
Logan, Queensland, Australia
Again, contrast this with how many CBT school researchers discuss supports people get or could get
I was first told this by my CFS doc in 1993! He tracked his patients, and the happily married patients did much better. However he also said something not covered here - the patients who were unhappy with their marriage did worse than single patients.
 

BruceInOz

Senior Member
Messages
172
Location
Tasmania
Yes, this is a generally positive sounding piece. But isn't it fascinating how in all of this sort of research the conclusions turn on the unsupported interpretation of the researchers. In this case we have, for example (and there are other similar examples)
The scores for
the individuals who can work outside the home
were lower, indicating less impairment, than
those of individuals who were unemployed or
on disability. This finding suggests that as
symptoms become more frequent and severe,
the ability to work outside the home declines.
My bolding is the bit I'm calling an unsupported interpretation, which in this case I happen to agree is quite plausible. But they don't have any evidence for this, they've just identified a correlation. A BPS proponent writing the same paper with the same evidence before them would probably have written "This finding suggests patients should be encouraged to remain in employment as it should lead to an improvement of their symptoms". Surely conclusions or inferences that turn on researcher interpretation are just not science.
 

alex3619

Senior Member
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13,810
Location
Logan, Queensland, Australia
Surely conclusions or inferences that turn on researcher interpretation are just not science.
They can be if stated as an hypothesis. They are not if stated as fact. "Suggests" is the critical word here. Unfortunately many who want to believe in a particular interpretation of findings will take "suggests" and reject or accept it as fact based on their own preconceptions.